Facet screw system and method

ABSTRACT

A facet screw system and method includes an implant assembly having a screw with a removable head, a locking nut, and a collet. An insertion instrument is used to insert the screw, compress the facet joint, locks the implant, and breaks off the head of the screw providing a lower profile implant.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/614,054 filed Jun. 5, 2017, which is a division of U.S. applicationSer. No. 13/657,826 filed Oct. 22, 2012, now U.S. Pat. No. 9,668,784issued Jun. 6, 2017, which claims the benefit of U.S. provisionalapplication No. 61/549,979, filed on Oct. 21, 2011, the completedisclosures of each of which, in their entireties, are herebyincorporated by reference.

BACKGROUND Technical Field

The embodiments herein generally relate to lumbar and cervical fusiondevices, and, more particularly, to a facet screw system and method usedin spinal surgeries.

Description of the Related Art

Conventional lumbar fusion, facet screws, facet fusion, and screwfixation systems include devices described in U.S. Pat. No. 6,485,518,U.S. Patent Publication No. 2005/0149030, and U.S. Patent PublicationNo. 2009/0192551, the complete disclosures of which, in theirentireties, are herein incorporated by reference.

SUMMARY

In view of the foregoing, an embodiment herein provides a novel screwmechanism that is used to immobilize the facet joint in order tofacilitate fusion in the human spine. The embodiments herein allow aninfinite degree of compression after the screw is fully inserted, whichprovides superior net fixation than fixed-head devices which allowcompression only by continued screw insertion after the screw head abutsthe cortical surface of the bone. The embodiments herein provide aninstrument which sequentially inserts the screw, compresses the facetjoint, and locks the system in place, with all of the steps performedwith only one implant/instrument engagement.

One embodiment provides a medical implant assembly comprising a bonesecuring component comprising a first part and a second part; a lockingmechanism positioned around the second part of the bone securingcomponent; and a holding mechanism positioned through the lockingmechanism and around the second part of the bone securing component. Thebone securing component may comprise a screw mechanism adapted to beinserted into the bone. The locking mechanism may comprise a locking nutcomprising a first set of threads. The holding mechanism may comprise acollet comprising a plurality of flexible flanges arranged in asubstantially radial configuration; a second set of threads that areconfigured to mate with the first set of threads of the locking nut; anda hole configured through a center of the collet. In one embodiment,each of the plurality of flexible flanges comprises an outwardlyprotruding end positioned at an end of the collet opposite to the secondset of threads. The first part of the bone securing component may beadapted to break off from the second part after insertion of the bonesecuring component into bone.

Another embodiment provides a medical apparatus used on a facet joint ina body, the apparatus comprising a bone securing component that engagesthe facet joint; a locking mechanism positioned around the bone securingcomponent; a holding mechanism positioned through the locking mechanismand around the bone securing component; and an insertion tool configuredto attach to the holding mechanism. The bone securing component maycomprise a screw mechanism adapted to be inserted into a bone of thefacet joint. The locking mechanism may comprise a locking nut comprisinga first set of threads. The holding mechanism may comprise a colletcomprising a plurality of flexible flanges arranged in a substantiallyradial configuration; a second set of threads that are configured tomate with the first set of threads of the locking nut; and a holeconfigured through a center of the collet. Each of the plurality offlexible flanges may comprise an outwardly protruding end positioned atan end of the collet opposite to the second set of threads. Theinsertion tool may comprise a shaft that engages the bone securingcomponent wherein rotation of the shaft causes rotation of the bonesecuring component, and wherein rotation of the bone securing componentcauses insertion of the bone securing component into the bone. Theinsertion tool may comprise means for applying compression on the facetjoint. The bone securing component may comprise a first part and asecond part, wherein the first part is adapted to break off from thesecond part after insertion of the bone securing component into a boneof the facet joint. The insertion tool locks the holding mechanism ontothe locking mechanism by inwardly forcing the plurality of flanges ofthe collet against the bone securing component. Moreover, the insertiontool also serves to allow the engagement and tightening of the lockingmechanism with the holding mechanism, which inwardly forces theplurality of flanges of the collet against the bone securing component.

Another embodiment provides a method of compressing a facet joint in abody, the method comprising inserting a medical implant into a bone inthe facet joint by rotating an insertion tool that holds the medicalimplant, wherein the medical implant comprises a bone securingcomponent, a locking mechanism positioned around the bone securingcomponent, and a holding mechanism positioned around the bone securingcomponent and through the locking mechanism; compressing the facet jointby pressing the insertion tool and the medical implant against the facetjoint; and locking the locking mechanism and the holding mechanismaround the bone securing component. The method may further comprisebreaking off a top part of the medical implant. The locking mechanismmay comprise a locking nut comprising a first set of threads. Theholding mechanism may comprise a collet comprising a plurality offlexible flanges arranged in a substantially radial configuration; asecond set of threads that are configured to mate with the first set ofthreads of the locking nut; and a hole configured through a center ofthe collet. Each of the plurality of flexible flanges may comprise anoutwardly protruding end positioned at an end of the collet opposite tothe second set of threads. The insertion tool may comprise a shaft thatengages the bone securing component, wherein rotation of the shaftcauses rotation of the bone securing component, and wherein rotation ofthe bone securing component causes insertion of the bone securingcomponent into the bone.

These and other aspects of the embodiments herein will be betterappreciated and understood when considered in conjunction with thefollowing description and the accompanying drawings. It should beunderstood, however, that the following descriptions, while indicatingpreferred embodiments and numerous specific details thereof, are givenby way of illustration and not of limitation. Many changes andmodifications may be made within the scope of the embodiments hereinwithout departing from the spirit thereof, and the embodiments hereininclude all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments herein will be better understood from the followingdetailed description with reference to the drawings, in which:

FIG. 1 illustrates a schematic diagram of an implant assembly accordingto an embodiment herein;

FIG. 2 illustrates an exploded view of an implant assembly according toan embodiment herein;

FIG. 3A illustrates a schematic diagram of the screw of an implantassembly according to an embodiment herein;

FIG. 3B illustrates a schematic diagram of the locking nut of an implantassembly according to an embodiment herein;

FIG. 3C illustrates a schematic diagram of the collet of an implantassembly according to an embodiment herein;

FIG. 4 illustrates a schematic diagram of an implant assembly incombination with an insertion instrument according to an embodimentherein;

FIG. 5 is a flow diagram illustrating a method according to anembodiment herein;

FIGS. 6A through 6C are schematic diagrams illustrating a screwinsertion process according to an embodiment herein;

FIGS. 7A through 7C are schematic diagrams illustrating a compressionprocess according to an embodiment herein;

FIG. 8 is a schematic diagram illustrating a lock and break off processaccording to an embodiment herein; and

FIGS. 9A through 9C are schematic diagrams illustrating a break offprocess according to an embodiment herein.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The embodiments herein and the various features and advantageous detailsthereof are explained more fully with reference to the non-limitingembodiments that are illustrated in the accompanying drawings anddetailed in the following description. Descriptions of well-knowncomponents and processing techniques are omitted so as to notunnecessarily obscure the embodiments herein. The examples used hereinare intended merely to facilitate an understanding of ways in which theembodiments herein may be practiced and to further enable those of skillin the art to practice the embodiments herein. Accordingly, the examplesshould not be construed as limiting the scope of the embodiments herein.

The embodiments herein provide a facet screw system and method thatinclude an implant assembly having a screw with a removable head, alocking nut, and a collet. An insertion instrument is used to insert thescrew, compress the facet joint, locks the implant, and breaks off thehead of the screw providing a lower profile implant. Referring now tothe drawings, and more particularly to FIGS. 1 through 9C, where similarreference characters denote corresponding features consistentlythroughout the figures, there are shown preferred embodiments.

Lumbar spine fusion using pedicle screws and rods is a widely popularprocedure in spinal surgeries. The pedicle screws and rods constructimmobilizes the spinal segment and hence facilitates fusion. Facetscrews are an alternative method of immobilizing the spinal segment. Theembodiments herein provide a system and method of immobilizing the facetjoint. The device is inserted through the facet joint and then it isused to apply compression to the facet joint. Finally, the device islocked in place. Hence, the device immobilizes the facet joint andenhances fusion in the spine. The device may be used to immobilize thefacet joint or it may be used to fix any other two bones.

FIG. 1 illustrates a schematic diagram of an implant assembly 100according to an embodiment herein. The assembly 100 includes a screw102, a locking nut 104 positioned around the screw 102, and a collet 106positioned through the locking nut 104 and around the screw 102.

FIG. 2 , with reference to FIG. 1 , illustrates an exploded view of animplant assembly 100 according to an embodiment herein. In this view thethreads 108 of the locking nut 104 are visible. The threads 108 of thelocking nut 104 engage the corresponding mating threads 110 of thecollet 106 upon insertion of the collet 106 into the locking nut 104.The collet 106 includes a plurality of flexible flanges 112 configuredin a substantially radial configuration such that the overallconfiguration of the collet 106 is substantially cylindrical and, in oneembodiment, is hollow. The collet 106 further includes a hole 114 orother means dimensioned and configured to receive the neck portion 120of screw 102.

FIG. 3A, with reference to FIGS. 1 through 2 , illustrates a schematicdiagram of the screw 102 of an implant assembly 100 according to anembodiment herein. The screw 102 includes a threaded portion 116, whichis dimensioned and configured to be able to anchor into bone 400 (ofFIGS. 6B and 6C). A substantially cylindrical central shaft 118 ispositioned on top of the threaded portion 116. A neck portion 120 ispositioned on top of the shaft 118, and a head 122 is positioned on topof the neck portion 120. In one embodiment, the neck portion 120 andhead 122 are hex-shaped.

FIG. 3B, with reference to FIGS. 1 through 3A, illustrates a schematicdiagram of the locking nut 104 of an implant assembly 100 according toan embodiment herein. The outer walls 125, which may be angled (e.g., ina hex configuration, for example), of the locking nut 104 aredimensioned and configured to be able to be gripped by an insertiontool. A bottom lip 124 is circumferentially disposed around the lowerportion of the locking nut 104.

FIG. 3C, with reference to FIGS. 1 through 3B, illustrates a schematicdiagram of the collet 106 of an implant assembly 100 according to anembodiment herein. The collet 106 also includes a central hole 126configured inside the radial configuration of the flanges 112. In oneembodiment, the collet 106 is configured having threads 110 which may beoptionally left-handed to engage with complementary threads of lockingnut 104 to tighten the collet 106 onto the neck portion 120 of screw102, allow for breakoff of head 122 of screw 102, and permit easyremoval of the assembly 100 after insertion, if necessary. The collet106 may be configured as any suitable type of holding mechanism, chuck,or collar device that provides for easy removal of the assembly 100after insertion, if necessary. In one embodiment, each of the flanges112 comprise a flat wall 140 adjacent to the threads 110, and aprotruding end 141 attached to the flat wall 140 such that theprotruding end 141 which outwardly protrude and extend beyond the planedefined by the flat wall 140.

FIG. 4 , with reference to FIGS. 1 through 3C, illustrates a schematicdiagram of an implant assembly 100 in combination with an insertioninstrument 200 according to an embodiment herein. The insertioninstrument 200 includes an engaging shaft 202, which may be hollow. Alocking handle 204 is operatively connected to the shaft 202. A button207 is connected to the shaft 202, and may be configured near theconnection of the locking handle 204 to the shaft 202, in oneembodiment. A compression knob 206 connects above the shaft 202 and isdisposed around a screwdriver 208. The screwdriver 208 may be positionedto extend through the shaft 202 to engage the assembly 100 and connectsto a handle 210 having a pair of gripping arms 212 (e.g., arranged in aT-shape configuration). A stabilizer 214 is positioned through thescrewdriver 208 and the shaft 202 and may be positioned above the handle210 and arms 212.

FIG. 5 , with reference to FIGS. 1 through 4 , is a flow diagramillustrating a method according to an embodiment herein. The methodincludes a three step approach including a screw insertion step 301followed by a joint compression step 303, and then followed by a lockingand break off step 305.

FIGS. 6A through 6C, with reference to FIGS. 1 through 5 , are schematicdiagrams illustrating the screw insertion process 301 according to anembodiment herein. The user (e.g., surgeon) holds the locking handle 204and rotates the handle 210 using the arms 212 as denoted by the enlargedarrows. The rotation of the handle 210 causes the screwdriver 208 andthe assembly 100 to rotate also, and the screw 102 is driven into thebone 400.

FIGS. 7A through 7C, with reference to FIGS. 1 through 6C, are schematicdiagrams illustrating a compression process 303 according to anembodiment herein. First, the insertion instrument 200 is pushed down(towards the bone 400). The final locking handle assembly (e.g., shaft202 and locking handle 204) is securely attached to the screwdriver 208.The assembly 100 is attached to the screwdriver 208 in such a way thatthe assembly 100 does not inadvertently slide down. However, theassembly 100 is free to rotate on the screwdriver 208. One pushes thebutton 207 to slide down the assembly 100 to engage the assembly 100with the locking nut 104. After the screw 102 is inserted, the userpushes the button 207 on the locking handle 204 and slides the handle204 down. The lower end of shaft 202 is dimensioned and configured(e.g., as an internal hex, for example) to engage the locking nut 104(e.g., engages the outer hex walls 125 of the locking nut 104, forexample) as the shaft 202 slides down. The user does not have to pushdown the entire instrument 200. The handle 204 is pushed down to engagethe shaft 202 with the locking nut 104.

Finally, the compression knob 206 is turned. Once the final lockinghandle assembly (e.g., shaft 202 and locking handle 204) is engaged withthe locking nut 104, the compression knob 206 is turned in order to pushshaft 202 down. This process applies additional compression on the facetjoint. This is why this step is called the compression step 303.

FIG. 8 , with reference to FIGS. 1 through 7C, is a schematic diagramillustrating a lock and break off process 305 according to an embodimentherein. The user holds the locking handle 204 and rotates the handle 210until the head 122 of screw 102 breaks off FIGS. 9A through 9C, withreference to FIGS. 1 through 8 , are schematic diagrams illustrating abreak off process 305 according to an embodiment herein. The assembly100 is shown with the head 122 attached to the screw 102 in FIG. 9A. Theinsertion instrument 200 is attached to the implant assembly 100 beforeinsertion. The head 122 is removed after break off occurs when the userpulls out the instrument 200. The head 122 is still attached to theinstrument 200 at this point, and then may be discarded.

The collet 106 can freely translate on the neck portion 120 and head 122(i.e., the hex regions) of the screw 102. The locking nut 104 ismatingly threaded on the collet 106 (e.g., threads 108, 110). Theassembly 100 is preferably pre-assembled before it is attached to theinsertion instrument 200. In the assembly 100, the locking nut 104 andcollet 106 are still able to translate freely prior to insertion by theinsertion instrument 200. The head 122 of the screw 102 has internalthreads 123 (shown in FIG. 2 ), which are configured to attach to thestabilizer 214 after the assembly 100 is attached to the screwdriver 208of the insertion instrument 200. The stabilizer 214 secures the screw102 to the screwdriver 208.

In the final step, the handle 210 is rotated to lock the collet 106 onthe screw 102. This is achieved by flexing (FIG. 3C shows thecollapsible nature of the collet 106) the flanges 112 of the collet 106on the screw 102 by advancing the locking nut 104. Once a thresholdtorque is applied, the head 122 of the screw 102 breaks off leaving thescrew assembly 100 in the patient without the unnecessary protrusion ofthe head 122 remaining.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the embodiments herein that others can, byapplying current knowledge, readily modify and/or adapt for variousapplications such specific embodiments without departing from thegeneric concept, and, therefore, such adaptations and modificationsshould and are intended to be comprehended within the meaning and rangeof equivalents of the disclosed embodiments. It is to be understood thatthe phraseology or terminology employed herein is for the purpose ofdescription and not of limitation. Therefore, while the embodimentsherein have been described in terms of preferred embodiments, thoseskilled in the art will recognize that the embodiments herein can bepracticed with modification within the spirit and scope of the appendedclaims.

What is claimed is:
 1. A method of immobilizing a facet joint in a body, the method comprising: inserting a medical implant into a bone in the facet joint, wherein the medical implant comprises a bone securing component, a locking mechanism, and a holding mechanism; compressing the facet joint using an insertion instrument, wherein the insertion instrument comprises a shaft configured to slide to engage the locking mechanism, wherein a compression knob of the insertion instrument is turned to push the shaft in a distal direction to apply compression to the facet joint; and breaking off a head of the bone securing component using the insertion instrument.
 2. The method of claim 1, wherein the bone securing component comprises a screw.
 3. The method of claim 1, wherein the locking mechanism comprises a locking nut.
 4. The method of claim 1, wherein the holding mechanism comprises a collet.
 5. The method of claim 4, wherein the collet comprises a plurality of flexible flanges arranged in a substantially radial configuration.
 6. The method of claim 1, wherein the step of compressing is performed after the bone securing component is fully inserted in the facet joint.
 7. The method of claim 1, wherein the compression knob is turned after the shaft is engaged with the locking mechanism.
 8. The method of claim 1, wherein the insertion instrument comprises a screwdriver.
 9. The method of claim 1, wherein the locking mechanism and the holding mechanism are able to translate freely prior to locking the locking mechanism and the holding mechanism around the bone securing component.
 10. A method of immobilizing a facet joint in a body, the method comprising: inserting a medical implant into a bone in the facet joint, wherein the medical implant comprises a screw, a locking nut, and a collet; compressing the facet joint using an insertion instrument, wherein the insertion instrument comprises a shaft configured to slide to engage the locking nut, wherein a compression knob of the insertion instrument is turned to push the shaft in a distal direction to apply compression to the facet joint; and breaking off a head of the screw using the insertion instrument.
 11. The method of claim 10, wherein the collet comprises a plurality of flexible flanges arranged in a substantially radial configuration.
 12. The method of claim 10, wherein the step of compressing is performed after the screw is fully inserted in the facet joint.
 13. The method of claim 10, wherein the compression knob is turned after the shaft is engaged with the locking nut.
 14. The method of claim 10, wherein the insertion instrument comprises a screwdriver.
 15. The method of claim 10, wherein the locking nut and the collet are able to translate freely prior to locking the locking nut and the collet around the screw. 